title: Natural evolution of nuchal thickness in trisomy-21 fetuses.
abstract: OBJECTIVE
  To assess the natural evolution of nuchal thickness in trisomy-21 fetuses.
  
  
  METHODS
  Serial measurements of nuchal thickness were performed over a 1- to 6-week period in 45 consecutive fetuses with trisomy 21, between the 10th and the 23rd weeks of pregnancy. To avoid a gestational age confounding effect, nuchal thickness also was expressed in standard deviations (SDs) for the corresponding gestational week. In addition, the changes were assessed in terms of the presence of clinical positive thickening, considered as such when the measurement was above 2.5 SD.
  
  
  RESULTS
  A mean increase of 1.8 mm (95% confidence interval [CI] 1.3, 2.3) for nuchal thickness was observed for a mean period of 21 days. When corrected by gestational age, the mean increase of 0.3 SD (95% CI -0.2, 0.9) was found to be not significant. No clinically relevant nuchal thickening changes were recorded (51% versus 69%) at re-examination.
  
  
  CONCLUSIONS
  Nuchal thickening at re-examination is observed in a similar proportion of trisomy-21 fetuses as when first observed.
authors.affiliation: Department of Obstetrics and Gynaecology, Hospital Clinic, University of Barcelona Medical School, Catalonia, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Borrell
authors.forename: D
authors.initials: D
authors.lastname: Costa
authors.forename: J M
authors.initials: JM
authors.lastname: Martinez
authors.forename: M T
authors.initials: MT
authors.lastname: Farré
authors.forename: J
authors.initials: J
authors.lastname: Cararach
authors.forename: A
authors.initials: A
authors.lastname: Fortuny
mesh_terms: D004314:Down Syndrome / Q000000981:diagnostic imaging / Q000196:embryology*; D005314:Embryonic and Fetal Development / Q000502:physiology*; D005260:Female; D005315:Fetal Diseases / Q000000981:diagnostic imaging / Q000196:embryology*; D005865:Gestational Age; D006801:Humans; D009333:Neck / Q000000981:diagnostic imaging / Q000196:embryology*; D011247:Pregnancy; D011446:Prospective Studies; D016216:Ultrasonography, Prenatal